FIG. 1 is a diagram of a wireless relay communication network architecture according to related technologies. As shown in FIG. 1, in a multi-hop radio relay system, one or more Relay Stations (RS) are arranged between a multi-hop relay Base Station (BS) and a Mobile Station (MS). The RS relays and transmits signals between the BS and the MS, in order to extend the coverage and increase the system capacity.
Based on the data forwarding mechanisms supported by RSs and the control capability of RSs on subordinate stations, RSs may be classified into Layer2 RS, which only supports air interface side function block, and Layer3 RS, which supports access network side function block. As the Layer2 RS only supports the two bottom-most layers (i.e., Physical (PHY) layer and Media Access Control (MAC) layer) in the network protocol architecture, the RS is directly or indirectly connected with the BS and controlled by the BS. For an Access Service Network Gateway (ASN GW), Layer2 RS does not exist. In contrast, in addition to PHY and MAC two layers, the Layer3 RS also supports an interface with the ASN GW, therefore, for the ASN GW, Layer3 RS is visible. In some standard protocols (for example, Institute for Electrical and Electronic Engineers (IEEE802.16m)), Layer3 RS is also called distributed control RS. As an evolved air interface standard based on IEEE802.16e System Profile Rel1.0, IEEE802.16m can provide complete backward compatibility for System Profile Rel1.0. To distinguish from the BS, RS, and MS in IEEE802.16e, the BS, RS, and MS in IEEE802.16m are called Advanced BS (ABS), Advanced RS (ARS) and Advanced MS (AMS).
The air interface addressing method in IEEE802.16m is different from that in IEEE802.16e. In IEEE802.16e, a Connection Identifier (CID) is used between the MS and the BS to identify a service flow; in IEEE802.16m, to reduce the overhead of the CID field in the Media Access Control Protocol Data Unit (MAC PDU), the CID is divided into two parts, respectively: the 12 bits Station Identifier (STID) and the 4 bits Flow Identifier (FID). During data transmission, the STID is carried in the resource indication evolved Advanced MAP (A-MAP) through Mask Cyclic Redundancy Code (MCRC), while the FID is carried in the MAC PDU.
In IEEE802.16e communication protocol, communication is performed between the BS and the ASN GW through R6 interface. In the R6 interface, the data plane transmission is encapsulated by means of Generic Routing Encapsulation (GRE). FIG. 2 is a diagram of a GRE encapsulation format based on Internet Protocol (IP) Convergence Sub-layer (CS) according to related technologies. As shown in FIG. 2, the GRE encapsulation format mainly contains the following fields:
Differentiated Service Code Point (DSCP), configured to indicate the Quality of Service (QoS) class of payload;
source/destination IP address, configured to indicate the endpoint of the GRE tunnel, for example, BS/ASN GW IP address;
GRE key, allocated by a specific node; usually, there is a one-to-one correspondence between the connection and the GRE key;
sequence number, configured to guarantee the synchronization and continuity of data transmission during the transmission process.
As shown in FIG. 2, GRE encapsulation format may further contain the following contents: IP Ver, IP HLEN, IP Datagram Total Length, IP Identification, IP Fragment Offset, IP Time to Live, IP Protocol, IP Header Checksum, GRE Payload Protocol Type or the like, which will not be described repeatedly herein.
FIG. 3 is a diagram of an access network data path based on IP CS according to related technologies. Specifically, FIG. 3 shows a function implementation method of a data path in an access network based on GRE encapsulation of IP CS. The BS and the ASN GW respectively perform mapping between the uplink and downlink connections and the GRE tunnel in IEEE802.16e, wherein, there is a one-to-one correspondence between the connection and the GRE key.
For Layer2 relay, during implementation, requirements on the functions of the RS are comparatively lower, but requirements on the functions of the BS are higher. Considering that signaling and data transmission methods completely different from those in traditional IEEE802.16e technology are required to be designed in the link (relay link) between the BS and the RS, therefore, during the product implementation, it is difficult to use existing software, and great difficulty is brought to the Interoperability Test (IOT). While for Layer3 relay, the RS is visible at the ASN GW, the RS may be directly controlled by the ASN GW. The BS plays a role of data and signaling forwarding between the RS and the ASN GW. In Layer3 relay, as functions of the RS and the BS are substantially similar, the only difference is that the function is weak or strong. Thus, the RS may use the existing software in the BS in IEEE802.16e repeatedly; no software has to be dedicatedly developed for the RS, so that the product development of the RS may be facilitated, and products may enter the market as soon as possible.
However, the information transmission method in the relay transmission network in the related technologies can not apply to the Layer3 RS, as a result, Layer3 relay transmission cannot be performed.